Weirdest Occurance of the infamous [3100] error code ever?

[Stayouttadabunker]

This one stumped me one time. 
I working the floor and walked up to an S+ Double Gold 2Cm (2x/4x/8x)
This is what I saw...>>> 

Top half of candle flashing medium speed.
"1" in the "Coins Played" window.
zero in the "Credits" window.
"Winner Paid" window displayed "160".
Alternating with the error code [3100].

What did I see wrong? haha

[knagl]

I think we're missing part of the story or a picture, but I'm guessing the reels had an orange 7, double, double on them?

[Stayouttadabunker]

yes...any7/ any7/ any7
I do recall the 1st reel with an orange 7...I don't remember what reel 2 or 3 had other than a variation of a 7.


Let me give it away....I thought the [3100] code should have been a result of an "extra coin paid" out and the winner paid window show "161" credits?
Why not display "161" instead of "160'?
I don't think I had ever solved this issue but it happens so rarely that I forget about when it happens.

I know the coin hopper was checked out and serviced and nothing was wrong with it.
The brakes were fine and the coin knife was in good order.
The hopper optics counted out in test mode 10 coins every time and the 3100 error could not be replicated.